1. Field of the Invention
The present invention relates to a silicon carbide semiconductor device including a field effect transistor to which a silicon carbide semiconductor is applied.
2. Description of the Related Art
Silicon carbide (described as “SiC” hereinafter) has a wide band gap and the maximum dielectric breakdown field strength thereof is one order of magnitude greater than that of silicon (described as “Si” hereinafter). Further, SiC is oxidized to be SiO2 in and, therefore, a thermal oxide layer can be easily formed on a surface of SiC in a similar method as in the case of Si. Therefore SiC is expected to be an excellent material when applied to high-speed/high-voltage switching devices, more particularly, high-power uni/bi-polar devices.
A planer type MOSFET is proposed as an application of SiC. A related art of the SiC planer type MOSFET is disclosed in Japanese Patent Application Laid-Open H10-233503. According to the disclosure, each unit cell of the SiC planer type MOSFET is provided with a P− type base region in a semiconductor substrate, an N+ type source region in the P− type base region and a gate electrode buried in an insulator layer formed on the P− type base region and the N+ type source region. A source electrode and a drain electrode are respectively electrically connected to the N+ type source region and the semiconductor substrate. When a positive voltage is applied to the gate electrode in a condition where the source electrode and the drain electrode are biased, inversion channel region is generated in the P− type base region in the vicinity of the gate electrode. Thereby current flow can occur from the drain electrode to the source electrode.